136 INTRODUCTION TO ZOOLOGY CHAP. 



Some Common Genera of Slugs. 



The genus Arion includes the common black 

 v ^ n g * n wo ds and gardens. The respiratory 

 aperture is in the front half of the mantle-shield ; 

 the shell is represented by a few calcareous grains under the 

 back part of the shield ; a slime gland is present in the tail. 



Arion ater if full grown may be 4 inches long when ex- 

 tended, but the body may be contracted into a lump (Fig. 87). 

 The tentacles are swollen at the tip, and black ; the colour 

 of the body varies, it may be black, brown, red, yellow, or 

 green ; the shield is lighter than the rest of the body ; the 

 foot usually has a yellow border. 



Arion hortensis is only J an inch long ; it is common in 

 gardens. The shell granules are compact, forming an oval 

 mass ; the body is marked with grey lines or stripes. 



Limax is the genus which includes the large grey 



Snax slug 8 - The shell is like a curved plate ; it is 



covered by the hind part of the mantle-shield, 



which has usually concentric lines on it. The respiratory 



opening is in the back half of the mantle-shield. The foot 



has no slime gland. 



Limax marginatus ( - Sowerbyi) is the Tree Slug ; the colour 

 of its body is yellow or reddish-brown with black speckles, 

 its slime is colourless, and its shell resembles shagreen. 



Limax flams (the Cellar Slug) is 4 inches long and yellow 

 with white and black specks ; it has yellow slime and a con- 

 centrically marked shield. 



Limax agrestis (the Grey Field Slug) is usually about -J of 

 an inch long and has a concentrically marked shield, an ash- 

 grey body, and milky slime. It is a very common and 

 destructive species, specially characteristic of damp spots. 



Limax maximus may be as much as 6 inches long ; its body 

 is grey with black spots, tentacles long and purple, and shield 

 regularly striate ; the shell is oblong and \ an inch long. 



This genus is peculiar amongst slugs in being 

 Testacella, . 



or the carnivorous ; it preys on worms and on smaller 



"Snail slugs and snails. It is also characterised by pos- 

 Slug." sessing a distinct ear-shaped shell, with a small 

 terminal spire of half a whorl. 



This shell and the mantle-shield below it are placed quite 



